Starter jaw advancing mechanism



Feb. 16, 1960 KALIKQW 2,924,979

STARTER JAW ADVANCING MECHANISNI Filed NOV. 10, 1955 United States Patent p 2,924,919 STARTER JAW ADVANCING MEcHANrsM Irving Kalikow, Swampscott, Mass., assignor to General ElectricCompany, a corporation of New York Application November 10, 195,5,1Serial No. 546,231 '5 Claims. (Cl. 74-7)l lrnitter to the starter upon starting a machine from rest.

The inertia screw advancing type of starter commonly used in starting machines, such as an engine, has an engaging jaw on one end of the armature or quill shaft which moves outwardly into engagement with the engine upon energization of the starter motor. The abrupt jolt created by the engaging action coupled with the application of heavy load forces, as represented by the dormant engine, transmits an initial shock to the motor and creates a twisting action on the armature shaft which is not completely compensated for in starters of the prior art. Friction damping devices of various design have been incorporated in starter motors forI absorbing such shock but they are invariably heavy and occupy valuablespacc where space is at a premium, as in an aircraft engine. Further difficulties have been encountered inobtaining withdrawal of the engaging jaw as it accelerates to an operating speed because of the engaging jaw cocks or hangs up on the armature shaft` thereby preventing retraction from the engine.

In carrying out my invention, I eliminate the abovecited disadvantages by providing a flexible member positioned within and connected to a starter motor shaft through a friction coupling at one end and having an advancing jaw at its other end for engaging an engine for starting, the exible member being constructed and arranged to absorb the shock of starting while the friction coupling acts to limit and control the extent of shock absorbed by the flexible member to a safe value. In practicing my invention in its broader aspects, it will occur to those skilled in the art that the mechanism may be incorporated in any kind of prime mover, although I specifically apply it to a motor, and the machine that it starts may be of any type susceptible of receiving its starting power from an exterior source.

For a more complete understanding ofthe invention, whichwill be more particularly pointed out in the appended claims, reference is now made to the following description taken in connection with the accompanying drawings in which:

Figure 1` is ayview in elevation, partly in section, showing the arrangement of parts when the starter is in an at rest position; and

Figure 2 is a fragmentary elevational view, partly in section, showing the arrangement of parts whenthe engaging jaw mechanism is in an engine engaged position.

Referring now-to the drawings wherein like reference characters designate like or corresponding parts throughout the several views, there is shown a starter illustrated as a dynamoelectric machine comprising a frame con- Itaining appropriate magnetic field elements, not shown, vand having end shields 12 and 14 respectively provided with bearing housings in which anti-friction bearings 16 2,924,979 Patented Feb. 16, 1960 and 18 are arranged for supporting a rotatable member. The end shield 14 is equipped with a hollow extension 15 which terminates in an outwardly projecting flange 17 arranged for physically attaching the starter to an engine. The rotatable member includes armature windings 20 connected to a commutator 22 which are mounted on a hollow armature or quill shaft 24 extending centrally through the rotatable member.

A flexible inner shaft or torque rod 26 is positioned concentrically within the quill shaft 24 and is provided with an upstanding collar 28 adjacent an end thereof as shown in Figure 1. In order to provide a driving connection between-quill shaft 24 and torque rod 26 which will absorb sudden shocks, a friction clutch or coupling is provided on the outboard end of the torque rod and is arranged to coact with the inner peripheral surface of quill shaft 24. l'

In the preferred form, the friction coupling comprises a set of splines 30 formed onthe end of the torque rod for receiving a cone damper 32 having an outer surface arranged for frictional contact with the inner peripheral surface of quill shaft 24. The cone damper 32 is firmly positioned on the end ofthe torque rod by a plate 36 pressed against the cone damper by a nut 38. In order to position the cone damper in lirm frictional relationship with the inner surface of the quill shaft, a b-iasing spring 42 is located between plate 36 and a spring tension adjusting cap 44 screw-threadedly attached tothe end of the quill shaft. It will be evident that the degree of frictional contact between the cone damper 32 and quill shaft 24 is governed by the extent of compression of spring 42. After the spring is initially compressed, the degree of compression would normally not be changed; however, it would be possible to make such a'change by merely turning the adjusting cap 44 in the `desired direction. The cap is prevented from moving relative to shaft 24 by a locking ring 46 having tabs which are kbent over in locking engagement with the cap.

The engaging end of the mechanism comprises a bearing member 48 arranged for aligning the torquerod within the quill shaft 24. The torque rod is provided with a plurality of spiral grooves 50 and terminates in integrally formed shoulders 51 and 52 machined on an end thereof. A. hollow` engaging jaw 54 arranged for longitudinal and rotary movement on the end of the torque rod, comprises a weighted portion 56 having engine engaging dogs 58 formed'on its outer end Yfor contacting mating grooves `fixed in an end of the engine. The cylindrical end 60, opposite-from the dogs, ts within the hollow quill shaft and is provided with internal spiral threads 61, welded or otherwise ajxed to the inner cylindrical surface, arranged to ride in the spiral grooves 50 when the torque rod is rotated by the motor, therby simultaneously imparting longitudinal and rotary motion to the engaging jaw 54.

Jamming or a hanging up of the engaging jaw on the torque rod during either an engaging or retracting action is prevented by a jaw aligning bearing 62 pressed in an end of the engaging jaw and being of a diameter just sulicient to permit easy sliding movement on the surfaceV appearing between shoulders 51 and 52. The engaging jaw 54 is held squarely on the torque rod 26 by the bearing 62 and by the top of the spiral threads on the torque rod which coact closely wit-h the cylindrical end 60 and threads 61 formed thereon. The coacting threads essentially form a bearing similar to bearing 62, for providing a smooth lit with a minimum ofradial play throughout all axial positions of the engaging jaw. Y

In order to return vthe engaging jaw 54 to its retracted position, a biasing spring 164 lbearing between anl end of the aligning bearing and shoulder 52 exerts sufficient force to retract the engaging jaw as soon as the engine becomes self-supporting. Atthe precise moment of disengagement, .no torque is being transmitted across the jaws, .that is, from the starter .motor to the 4engine and vice versa, thereby enabling the .spring to separate the engaged members. This action will take .place even though the .starter may continue to run at .full speed. It is to be noted that continued .running fof the starter, even at full speed, will not advancethe jaw ,to an engaged position since the jaw is moved only during .an initial acceleration period.

Operation In operation, energization ofthe dynamoelectricmachine causes torque to be transmitted through the quill shaft24, cone damper '32, torque'rod 26 and engaging jaw 54 lto anengine or other machine arranged for=starting. Upon initiation'o'f rotation ofthe torque rod, the threads Itil on the cylindrical end of engaging jaw`54 are caused to travel in the spiral grooves 50 thereby -causing the engaging jaw to move laterally -'to -the -right against the fforce 'of spring 64. 'The jaw reaches ritsffexten'ded posiftion when shoulder 52` is in firm contact with the flat seat 53 formed on lthe outer end of'jaw 54 and, at this time, the dogs 58 are in a position to effectively transmit torque from'the starter to the engine.

It will be evident .that .motors employed `for starting engine vor other machines fromrest have extremely high `4starting torques and as a consequence, the engaging jaw is -accelerated at a-high-rate and is caused to-contact its mating part in the engine with an impact that, in this structure, is due only to the inertia of the engaging jaw and not the complete starter armature. This engaging jaw inertia effect is of very short duration, lasting a period of timenecessary for the establishment of iirm con- -tact between surfaces 52 and '53 and proper engagement of the jaw lwith the engine. At this instant, the starter "motor will be at or near full speed while the engine is "at a standstill and in order to absorb the instantaneous lshock transmittedto the-starter, the torque vrod 26 will twist a suiiicient amount to dissipate the forcewhich in jprior art devices might shear the shaft. The limit of jtorque rod twist is controlled rto a safe value by the friction clutch or coupling which simultaneously trans- `mits the full youtput torque ofthe starter motor. A 1kuniquefunction performed by the torque rod and friction coupling, as opposed to devices utilizing friction clutches fonly, is that the shockwave starts lfrom zero, since `all "spring loadings start "from zero, land builds up to a pre- A:determined limit. A pure friction-'device lon the `other jhantlystarts with full impact shockf'vequivalent to the @friction setting which vcontributes to severe' wear of the jen'gagingjaws Aand supporting mechanism. 'Thus-it will structures,'are damped `and severely limitedby .the shock :absorption devices acting in the mannerdescribed above.

A :cockng action of the `engaging jaw ,on the torque 4rod .or :quill shaft, yresulting 4in a jamming of the mech- -;anism,-.is prevented by virtue of themachined surfaces #provided ton .the 'coacting parts .thereby assuring proper engagement and retraction'underall .conditions 'of operation as explainedabove Y y-Obviously many irnodications and :variations of the lpresent invention-aregrpossible in lightof the .above teachings. It is therefore to be understood that within: the

scope ofthe appended claims the invention may be practiced otherwise than as specifically described.

What I claim as new andl desire to secure by Letters Patent of the United States is:

1. A starter jaw advancing mechanism for use with a prime mover utilized in starting a machine comprising a hollow shift arranged to transmit torque supplied by said prime mover and a exible torque rod concentrically positioned in said hollow shaft, Vfriction damping means mounted on said torque rod and interconnecting one end thereof with an internal surface of said shaft, a major portion of said vdamping `means being `wholly positioned within said shaft, .and spring means permanently biasing said damping means into frictional sliding contact with the internal shaft surface so that slippage between said torque rod and shaft will occur when the relative turning forces therebetween .ex,ceeds.;the `frictional forces presented by the .damping `meanaa'n.engaging jaw slidably mounted on .said torque .rod `at its other end for transmitting torque ,from .said hollow shaft `and torque `rod to said machine, and centering Imeans comprising mutually coacting bearing surfaces onsaid engaging jaw and said .torque rod for providingsmooth and uninterrupted movement of said engaging jaw Vinto engagement with said ,machine inresponse to ,actuation of said torque rod.

2, A starter jaw advancing mechanism for use with a prime mover utilized in .starting a `machine comprising aflexible .torque rod having its torsional length concentrically positioned whollywitliin a'hollow shaft connected with said prime mover, friction ,damping means interconnecting one end of said torque rod with said hollow shaft, said damping ,means comprising a cone damper atlixed to said Atorque .rodand .having an outer surface in frictional contact with the ,inner y peripheral surface of said hollow shaft, an engaging jaw `spring biased to a disengaged .position on .the vother end of Vsaid torque rod projecting vslightly .beyond the end vof said shaft and arranged to be thrown `outwardly into engagement with said machine uponrotation of said torque rod, and combined stop and 'centering means V`compris- .ing coacting bearing surfacesrespectively .fixed 4on said engaging jaw.and said torque rodfor .providinglimited .movement and uninterrupted .engagement and ,retraction of said engaging jaw with saidfmachine.

3. The combination accordingto vclaim 2 4wherein Ysaid friction :dampingmeans further ,comprises aspiring tension adjusting cap.detachably`,mounted onpan end` of said Yhollow shaft, and aretainingslprirligy positioned between said `capandsaid conetdampertforurging said damper into .frictional `engagement with.,said ,inner 1peripheral .surface .of-.said hollowfshaft `with.a-force corresponding Ito theamountof tension created. insaidspringby the adjusting cap. p

4. An .electric Y"starter, for -use ,in starting machines comprising a hollow shaft supporting .a rrotor for a dynmoelectric machine, aflexible ,torquerod concentrically positioned within saidhollow shaft and friction .dampingsmeans interconnecting one end vof said torque rod with the inner peripheral surface of saidhollow shaft so that upon rotation of said rotor torqueis transmitted .through said hollow shaft and said friction damping means to said torque rod, an engaging jaw onthe other end of said torque rod arranged to be thrown `outwardly into engagement withsaidmachineupon -rotation of Asaid rotor, said .engaging jaw Acomprising a weighted memberhaving spaced dogs on one Yendthereof adapted for engagement with saidmachine,.an-axially extending ycylindrical'portion having internal spiral vgrooves formed 5 bla of pfviding smooth and uninterrupted axial movement of the engaging jaw with said machine and biasing means coacting with said torque rod and said engaging jaw for biasing the latter into a disengaged posi tion. v f

5. The combination according to claim 4 wherein said 'torque rod is provided with stop means integrally formed thereon and engageable by said engaging jaw when the latter is thrown outwardly for engagement with said machine.

References Cited in the Ele of this patent UNITED STATES PATENTS Meyers Dec. 6, 1927 Clouston June 18, 1940 Berges July 9, 1940 Bergman Nov. 5, 1940 Kalikow Nov. 10, 1953 FOREIGN PATENTS Germany June 19, 1931 

